Effect of hybrid pin tool-induced heat input on friction stir welded Al–Cu joints for electrical busbar applications

Dissimilar Al/Cu joints are increasingly used in electrical busbars and related applications due to their lightweight and high electrical conductivity. Although friction stir welding (FSW) is a solid-state joining technique, brittle intermetallic compound (IMC) formation during welding still limits Al/Cu joint performance. The present study investigated Al 1050 and Cu 11000 plates joined using FSW with a newly developed hybrid pin tool under three different heat input (ω/ν ratio) conditions [high (HH), intermediate (IH) and low (LH)]. The results demonstrated that heat input significantly influenced the material flow behaviour and IMC formations within the stir zone, which consequently affected the electrical and mechanical properties of the joints. SEM–EDS analysis confirmed the formation of IMC like Al2Cu and Al4Cu9, at the stir zone. Among the investigated conditions, the joint fabricated under LH condition showed the highest tensile strength of 66.57 ± 3.2 MPa, whereas the maximum hardness values were observed in the joints produced under HH conditions. The electrical resistivity of welded joints produced under different heat input conditions ranged from 2.37 ± 0.12 µΩ·cm to 3.04 ± 0.20 µΩ·cm. The results obtained demonstrate that FSW can be used to produce Al–Cu joints suitable for electrical applications under low heat input welding conditions.